I copied a sheet named MLiq in a local matrix named Liq with this instruction

Liq = MLiq.getDataRange().getValues() 

In a for cycle I'm workin in these cells value Es. Liq[i+1][1] = Liq[i+1][2] + Liq[i+1][3] How can I fixed the round off to n numbers after dot in the Liq[i+1][1] value? I tried toFixed but it change the format from number to string.